Re: st: transform observations in variables

[Nick Cox <n.j.cox@stata.com>]

An alternative is

egen period1 = mean(size) if period == 1, by(familyname)
bysort familyname (period1) : replace period1 = period1[1]


So this can be generalised to

forval i = 1/3 {
	egen period`i' = mean(size) if period == `i', by(familyname)
	bysort familyname (period1) : replace period`i' = period`i'[1]
}

That should deal more smoothly with repeats (if any) and gaps.

Nick
n.j.cox@durham.ac.uk

Nick Cox wrote:
> Consider -period- 1. Then
>
> (period == 1) * size
>
> is 0 when -period- is not 1 and -size- when -period- is 1. So
>
> egen period1 = total((period == 1) * size), by(familyname)
>
> should do the trick so long as -period- is 1 just once for each family.
>
> Similarly, the other -period- values should fall to the same trick:
>
> forval i = 1/3 {
>     egen period`i' = total((period == `i') * size), by(familyname)
> }
>
> Now one problem is apparent: family AB for example is not observed at
> periods 2 and 3. So -period2- and -period3- will be 0 for that family.
> If -size- can only be positive, then no problem: 0 means missing, and 
> that can be fixed.
>
> If -size- can be zero, then some other solution will be needed.
>
> If each value of -period- can occur more than once for each family, then 
> that is soluble, but I'll wait to hear that can happen.
>
> Nick
> permanent address:n.j.cox@durham.ac.uk
>
>
> Fabian Brenner
>
> My data look like the following:
>
> "familiyname"    "period"     "size"        "period1"      "period2"
>   "period3"
>
> AA                    1              8
> AA                    2              7
> AA                    3              3
>
> AB                    1               4
>
> BG                    1               4
> BG                    2               8
>
> For each "familyname" I want to get the values of "size" in the column
> with the equivalent "period" (1 to 3). The values of "size" should be
> written in the column of the equivalent period for all observations of
> the same "familyname" (that is why I wasn't able to manage it with -if-)
>
> The result should be:
>
> "familiyname"    "period"        "size"            "period1"
> "period2"          "period3"
>
> AA                    1              8                  8
>    7                     3
> AA                    2              7                  8
>    7                     3
> AA                    3              3                  8
>    7                     3
>
> AB                    1               2                  2
>
>
> BG                    1               4                  4
>     6
> BG                    2               6                  4
>     6
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